As a result of introducing so-called "Just-in-Time" manufacturing systems, and "Inventory-on-wheels" systems which use global positioning systems (GPS), many companies now have more products in transit than in their warehouses. Consequently, thefts of and from tractor-trailers, shipping containers and the like are increasingly a major security problem.
Security devices for tractor-trailers and transportation containers are known. For example, U.S. Pat. No. 5,475,362 discloses an alarm system for tractor-trailers which employs sensing switches which trigger the alarm when actuated, such as by the unauthorized opening of a door, and may also disable the vehicle. U.S. Pat. No. 5,615,247 discloses a security device for cargo transport containers which employs a pair of cables threaded through the door handles of the container. If the cables are cut or disconnected, the security device uses a cellular radio network to send an alarm signal to a security company. A disadvantage of these arrangements is that they protect only against conventional access, such as through doors, and are visible from inside or outside the container.
For one aspect of the present invention, an object is to mitigate this problem and provide a security device for sealed enclosures or containers which is capable of detecting access by any route. For another aspect of the invention, an object is to provide covert apparatus for monitoring opening of sealed enclosures.